harmony 鸿蒙UIAbility组件基本用法

2022-12-13
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UIAbility组件基本用法

UIAbility组件的基本用法包括：指定UIAbility的启动页面以及获取UIAbility的上下文UIAbilityContext。

指定UIAbility的启动页面

应用中的UIAbility在启动过程中，需要指定启动页面，否则应用启动后会因为没有默认加载页面而导致白屏。可以在UIAbility的onWindowStageCreate()生命周期回调中，通过WindowStage对象的loadContent()方法设置启动页面。

import { UIAbility } from '@kit.AbilityKit';
import { window } from '@kit.ArkUI';

export default class EntryAbility extends UIAbility {
  onWindowStageCreate(windowStage: window.WindowStage): void {
    // Main window is created, set main page for this ability
    windowStage.loadContent('pages/Index', (err, data) => {
      // ...
    });
  }
  // ...
}

说明： 在DevEco Studio中创建的UIAbility中，该UIAbility实例默认会加载Index页面，根据需要将Index页面路径替换为需要的页面路径即可。

获取UIAbility的上下文信息

UIAbility类拥有自身的上下文信息，该信息为UIAbilityContext类的实例，UIAbilityContext类拥有abilityInfo、currentHapModuleInfo等属性。通过UIAbilityContext可以获取UIAbility的相关配置信息，如包代码路径、Bundle名称、Ability名称和应用程序需要的环境状态等属性信息，以及可以获取操作UIAbility实例的方法（如startAbility()、connectServiceExtensionAbility()、terminateSelf()等）。如果需要在页面中获得当前Ability的Context，可调用getContext接口获取当前页面关联的UIAbilityContext或ExtensionContext。

在UIAbility中可以通过this.context获取UIAbility实例的上下文信息。

  import { UIAbility, AbilityConstant, Want } from '@kit.AbilityKit';

  export default class EntryAbility extends UIAbility {
    onCreate(want: Want, launchParam: AbilityConstant.LaunchParam): void {
      // 获取UIAbility实例的上下文
      let context = this.context;
      // ...
    }
  }

在页面中获取UIAbility实例的上下文信息，包括导入依赖资源context模块和在组件中定义一个context变量两个部分。

  import { common, Want } from '@kit.AbilityKit';

  @Entry
  @Component
  struct Page_EventHub {
    private context = this.getUIContext().getHostContext() as common.UIAbilityContext;

    startAbilityTest(): void {
      let want: Want = {
        // Want参数信息
      };
      this.context.startAbility(want);
    }

    // 页面展示
    build() {
      // ...
    }
  }

也可以在导入依赖资源context模块后，在具体使用UIAbilityContext前进行变量定义。

  import { common, Want } from '@kit.AbilityKit';

  @Entry
  @Component
  struct Page_UIAbilityComponentsBasicUsage {
    startAbilityTest(): void {
      let context = this.getUIContext().getHostContext() as common.UIAbilityContext;
      let want: Want = {
        // Want参数信息
      };
      context.startAbility(want);
    }

    // 页面展示
    build() {
      // ...
    }
  }

当业务完成后，开发者如果想要终止当前UIAbility实例，可以通过调用terminateSelf()方法实现。

  import { common } from '@kit.AbilityKit';
  import { BusinessError } from '@kit.BasicServicesKit';

  @Entry
  @Component
  struct Page_UIAbilityComponentsBasicUsage {
    // 页面展示
    build() {
      Column() {
        //...
        Button('FuncAbilityB')
          .onClick(() => {
            let context = this.getUIContext().getHostContext() as common.UIAbilityContext;
            try {
              context.terminateSelf((err: BusinessError) => {
                if (err.code) {
                  // 处理业务逻辑错误
                  console.error(`terminateSelf failed, code is ${err.code}, message is ${err.message}.`);
                  return;
                }
                // 执行正常业务
                console.info(`terminateSelf succeed.`);
              });
            } catch (err) {
              // 捕获同步的参数错误
              let code = (err as BusinessError).code;
              let message = (err as BusinessError).message;
              console.error(`terminateSelf failed, code is ${code}, message is ${message}.`);
            }
          })
      }
    }
  }

获取UIAbility拉起方的信息

拉起方（UIAbilityA）通过startAbility启动目标方（UIAbilityB）时，UIAbilityB可以通过parameters参数获取UIAbilityA的Pid、BundleName和AbilityName等信息。

通过点击UIAbilityA中的”拉起UIAbilityB”按钮，拉起UIAbilityB。

import { common, Want } from '@kit.AbilityKit';
import { BusinessError } from '@kit.BasicServicesKit';


@Entry
@Component
struct Index {
  @State message: string = 'Hello World';
  @State context: common.UIAbilityContext = this.getUIContext().getHostContext() as common.UIAbilityContext;


  build() {
    Scroll() {
      Column() {
        Text(this.message)
          .id('HelloWorld')
          .fontSize(50)
          .fontWeight(FontWeight.Bold)
          .alignRules({
            center: { anchor: '__container__', align: VerticalAlign.Center },
            middle: { anchor: '__container__', align: HorizontalAlign.Center }
          })
          .onClick(() => {
            this.message = 'Welcome';
          })
        Button('terminateSelf').onClick(() => {
          this.context.terminateSelf()
        })


        Button('拉起UIAbilityB').onClick((event: ClickEvent) => {
          let want: Want = {
            bundleName: this.context.abilityInfo.bundleName,
            abilityName: 'UIAbilityB',
          }


          this.context.startAbility(want, (err: BusinessError) => {
            if (err.code) {
              console.error(`Failed to startAbility. Code: ${err.code}, message: ${err.message}.`);
            }
          });
        })
      }
    }
  }
}

在UIAbilityB的onCreate生命周期中，获取并打印UIAbilityA的Pid、BundleName和AbilityName。

import { AbilityConstant, UIAbility, Want } from '@kit.AbilityKit';
import { window } from '@kit.ArkUI';


export default class UIAbilityB extends UIAbility {
  onCreate(want: Want, launchParam: AbilityConstant.LaunchParam): void {
    // 调用方无需手动传递parameters参数，系统会自动向Want对象中传递调用方信息。
    console.log(`onCreate, callerPid: ${want.parameters?.['ohos.aafwk.param.callerPid']}.`);
    console.log(`onCreate, callerBundleName: ${want.parameters?.['ohos.aafwk.param.callerBundleName']}.`);
    console.log(`onCreate, callerAbilityName: ${want.parameters?.['ohos.aafwk.param.callerAbilityName']}.`);
  }


  onDestroy(): void {
    console.log(`UIAbilityB onDestroy.`);
  }


  onWindowStageCreate(windowStage: window.WindowStage): void {
    console.log(`Ability onWindowStageCreate.`);


    windowStage.loadContent('pages/Index', (err) => {
      if (err.code) {
        console.error(`Failed to load the content, error code: ${err.code}, error msg: ${err.message}.`);
        return;
      }
      console.log(`Succeeded in loading the content.`);
    });
  }
}